We have performed high-resolution photoemission spectroscopy on MgB2 and observed opening of a superconducting gap with a narrow coherent peak. We found that the superconducting gap is s like with the gap value ( Delta) of 4.5+/-0.3 meV at 15 K. The temperature dependence (15-40 K) of the gap value follows well the BCS form, suggesting that 2Delta/k(B)T(c) at T = 0 is about 3. No pseudogap beha...

We succeeded in the synthesis of high-Jc MgB2 bulks via high energy ball-milling of elemental Mg and B powder at ambient temperatures. Alternatively to longtime mechanical alloying technique, the mixed powder was ball-milled for only 1h and the completed reaction is achieved by subsequent annealing. The correlations among synthesis parameters, microstructures and superconducting properties in M...

Cryogenic scanning tunneling microscopy and magnetization measurements were used to study the superconducting properties of MgB2. The magnetization measurements show a sharp superconductor transition at Tc = 39K, in agreement with previous works. The tunneling spectra exhibit BCS gap structures, with gap parameters in the range of 5 to 7 meV, yielding a ratio of 2∆/kBTc ∼ 3− 4. This suggests th...

We report on syntheses and electron transport properties of polycrystalline samples of diborides (AB2) with different transition metals atoms (A=Zr,Nb,Ta). The temperature dependence of resistivity, ρ(T ), and ac susceptibility of these samples reveal superconducting transition of ZrB2 with Tc = 5.5 K, while NbB2 and TaB2 have been observed nonsuperconducting up to 0.37 K. Hc2 (T) is linear in ...

Thermally-activated flux flow (TAFF) resistivity above the irreversibility field Bi is reported for two different c-axis textured MgB2 superconducting films. Transport measurements at different perpendicular magnetic fields 0,B,9 T and temperatures from 5 to 40 K reveal TAFF Ohmic resistivity rsT ,Bd for B.Bi described by the Arrhenius law, r=r0 exps-U /Td with the quadratic field dependence of...

Energy band structures are calculated for the new superconductor MgB2 and the related compounds by using the LDA and an FLAPW method. It is found that the strong three dimensional network in low-lying π bands brings about two dimensional σ holes in MgB2, which should be responsible for the superconductivity. The de Haas-van Alphen frequencies and the cyclotron masses are obtained for the Fermi ...

With the motivation of searching for new superconductors in the Mg-B system, we performed ab initio evolutionary searches for all the stable compounds in this binary system in the pressure range of 0-200 GPa. We found previously unknown, yet thermodynamically stable, compositions MgB3 and Mg3B10. Experimentally known MgB2 is stable in the entire pressure range 0-200 GPa, while MgB7 and MgB12 ar...

We substantiate by numerical and analytical calculations that the recently discovered superconductivity below 4 K in 3% boron-doped diamond is caused by electron-phonon coupling of the same type as in MgB2, albeit in three dimensions. Holes at the top of the zone-centered, degenerate sigma-bonding valence-band couple strongly to the optical bond-stretching modes. The increase from two to three ...

It has recently been observed that MgB2 is a superconductor with a high transition temperature. Here we propose a model of anisotropic s-wave superconductivity which consistently describes the observed properties of this compound, including the thermodynamic and optical response in sintered MgB2 wires. We also determine the shape of the quasiparticle density of states and the anisotropy of the ...

Superconducting MgB2 thin films have been fabricated by 80 keV B ion implantation into commercial Mg ribbon with B doses up to 10 ions/cm, followed by thermal annealing at 500 °C. Temperature dependent dc magnetization measurements confirmed superconducting phase transitions between 11 and 18 K for samples containing nanocrystalline MgB2 grains embedded in Mg substrate with a small amount of Mg...